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Introduction
The aim of this analysis is to describe the morphology of a hominin cranium; to record
measurements taken on it; and to compare the hominin skull with a modern one using these
morphological descriptions and measurements. This report starts off with some background
information on the hominin and modern skulls. The general preservation condition will be
assessed in the following section. Sex and age of the individual will then be inferred from the
cranial morphology. In the fourth section, morphological information of the hominin cranium
will be described and it will be compared to that of the modern skull. Lastly, measurements
will be listed and interpreted to allow numerical comparisons. This constitutes a less
subjective and perhaps more accurate way of comparing two crania.
Background Information
The hominin cranium examined in this paper is a Homo habilis skull (KNM-ER 1813).
Kamoya Kimeu discovered the skull at East Lake Turkana (previously known as East Lake
Rudolf), in northern Kenya (Leakey 1974:655). The site is known for its rich deposit of
hominin skeletons and archaeological material. The remains of over 130 hominins have been
recovered from there since excavations began in 1968 (Phenice and Sauer 1977:54).
Associated stone implements were also found at the location (Phenice and Sauer 1977:53).
KNM-ER 1813 was a very fractured cranium with a number of missing parts. The left side of
the cranium is also distorted, plausibly a consequence of pressure being exerted on the skull
during the fossilisation process (Smithsonian Institution n.d.). To contrast theH. habilis skull
with modern human crania, a modern European male skull was chosen at random.
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General Preservation Condition
KNM-ER 1813 is incomplete. The left zygomatic bone, together with the thin bone
connecting it with the supra-auricular bone, is missing (Figure 1). Although what is
presumably most of the right cheekbone is present, the thin bone connecting that and the
supra-auricular bone is again not present (Figure 2). Thus the actual breadth of the cheeks is
unknown and the measurement of bizygomatic breadth shown in this analysis would just be
estimation. The left side of the skull behind the face has a couple of missing fragments
(Figure 2). Moreover, a rather large area of the bottom of the skull is missing (Figure 3).
Hence, the location of the foramen magnum is uncertain. Upon inspecting the teeth, it is
found that the left incisors are missing and the teeth on the right side are eroded (Figure 4).
Figure 1. KNM-ER1813 (left) Figure 2. KNM-ER 1813 (right)
Figure 3. KNM-ER 1813 (bottom) Figure 4. The teeth of KNM-ER 1813.
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The cranium in general is very fractured. Some bone fragments of the reconstructed model do
not match perfectly (Figure 5), therefore the cranial measurements may not be entirely
accurate. Also, because of the fragmented nature of the skull, some sutures are ill-defined.
The left side of the face of the cranium is deformed (Figure 6). The top outer corner of the left
orbit is crushed, affecting the assessment of the actual shape of the orbits. (With the left
cheekbone missing, the actual shape of the orbit is hard to tell.)
Inferred Sex and Age of the individual
The cranium is classified as a male. The general robusticity of the skull, its relatively large
nuchal chest, pronounced temporal lines and prominent glabella, supra-orbital margin and
ridges all support this classification. The only feature that suggests the identification as a
female is the small mastoid processes. Despite the fact that the individual possesses small
mastoid processes, the hominin skull is still identified as a male because it is highly probable
that the mastoid processes might have been worn down, as suggested by missing parts near
the mastoid processes and the difference in size of the left mastoid process and the right
mastoid process.
Figure 5. KNM-ER 1813 (Top) Figure 6. KNM-ER 1813 (front)
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KNM-ER 1813 belongs to an adult (20-35) as the third molar has erupted. The tooth shows
moderate tooth wear, suggesting that the individual is around 25-30 years old. The fact that
the cranial sutures are all fused also indicates that the individual is an adult.
Cranial Morphological Description: Description
The vault of the hominin skull is relatively large in terms of skull proportions. The rather
robust vault is also long, narrow and round other than the somewhat protruding occipital area.
The cranial sutures are evidently fused, yet their complexity cannot be deduced as the
cranium is too fragmented for all sutures to be presented clearly. The glabella is large and
prominent. The brows are large in the center (in terms of facial proportions) and gradually get
smaller towards the sides. They are also continuous, arched and protruding. The frontal is
high and rounded. There is no sagittal keel. The parietal is also quite round with distinct
temporal lines. Parietal torus is absent. The temporals are relatively high considering the skull
proportions. The occipital is angular and somewhat projecting with an occipital torus present.
The mastoid processes are small, short and robust. However, it should be noted that the short
and small-sized mastoid processes could have been a result of weathering and erosion. There
is a large part missing at the bottom of the skull at the area of the foramen magnum, therefore
the shape of the foramen magnum is uncertain. But judging from the right side, the almost
intact side, of the foramen magnum and the estimated locations of the basion and opisthion,
the foramen magnum is likely to be circular.
The face of the hominin skull is relatively small and short, although it is fairly broad
considering the size of the skull. A rather pronounced projection below the nose is observed.
Having examined the non-skewed right orbit, it is reasoned that the orbits of KNM-ER 1813
should be round as they are in the shape of deformed circles. This distortion might be
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attributed to the high degree of fragmentation. The orbits are relatively small, taking up about
one quarter of the face. The borders of the orbits appear to be sharp, although this again might
be due to the fact that the skull is highly fractured. The nasal aperture is large and rather
round. The nasal bones are flat and indistinct. The malars are robust. With reference to the
fact that the left cheekbone is missing and that the right zygomatic bone may have broken off,
the broadness of the cheeks of the individual cannot be asserted.
The teeth are quite large. Upon inspection, it is found that the teeth on the left side are well
preserved except the two missing upper left incisors; while the teeth on the right side are
barely observable, with most parts of the teeth eroded away, only the roots and the complete
crown of the second molar remain. After examining the teeth on the left side, it is found that
the teeth show moderate wear.
There are five discernible foramina on the skull: the supra-orbital foramina directly under the
brows, incisive foramen (located behind the incisors), the greater palatine foramen near the
third molar on the right side and the foramen magnum.
Cranial Morphological Description: Comparison
When compared with the modern European male skull, the vault of the H. habilis skull is
relatively smaller. The vaults of the two crania are of similar relative length in terms of skull
proportions, but the hominin cranium is narrower. It is also more robust than the modern
cranium. While both vaults are quite round (Figures 1 and 7), the angle of curvature of the
modern skull is more like a 90 curve (Figure 7) whereas the curve of the vault of the hominin
skull is much smoother (Figure 1). The sutures of the modern European male skull are also
fused. However, due to the obscurity of the sutures of KNM-ER 1813, the complexity of the
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sutures cannot be compared. The glabellas of the two skulls are of similar size, but the
glabella of the hominin skull is more prominent (Figures 6 and 8). The brows are larger (with
facial proportions taken into account). The brows of both skulls are arched. Although instead
of being non-continuous like those of the modern cranium, the brows of the hominin cranium
are continuous. The frontal of KNM-ER 1813 is lower, flatter than that of theH. sapiens skull
(Figures 1 and 7). Both frontals are not keeled (Figures 1 and 7). No parietal torus is found on
either skull, yet it is also noted that the modern parietal is slightly more angled than the
hominin one (Figures 1 and 7). In spite of the fact that both skulls belong to male individuals,
the temporal lines on KNM-ER 1813 are longer and more distinct (Figures 1 and 7). The
temporals of the hominin cranium are higher (Figures 1 and 7). The occipital of the hominin
skull has a marked torus and is therefore angled and somewhat protruding; there is no torus
on the occipital of the modern cranium and it is round and non-projecting (Figures 1 and 7).
Apparently, the modern skull has larger mastoid processes despite the fact that both skulls are
identified as male. Nevertheless, the small mastoid processes of the hominin cranium might
have resulted from weathering and erosion. The shape of the foramen magnum of the modern
skull is a vertical oval (Figure 9), whereas the deduced shape of the foramen magnum of
KNM-ER 1813 is round.
Figure 7. Modern European Male skull (left) Figure 8. Modern European Male skull (front)
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TheH. habilis skull has a relatively larger, longer and broader face when compared with the
modern European male skull (Figures 1 and 7). It is also more projecting below the nose
(Figures 1 and 7). The orbits of the modern skull are square instead of circles like those of
KNM-ER 1813 (Figures 6 and 8). They are also bigger and smoother-bordered. The nasal
aperture of the hominin cranium is comparatively larger and more round (Figures 6 and 8).
While the nasal bones of the modern human skull are keeled and quite prominent; those of the
hominin skull are flat and rather indistinct (Figures 6 and 8). The malars of the hominin
cranium are less gracile than those of the modern cranium (Figures 6 and 8). The broadness of
the two crania cannot be compared as the left cheekbone of KNM-ER 1813 is missing and the
right cheekbone may have been eroded.
Comparing the teeth on the left side of the skulls (as the teeth on the right side of KNM-ER
1813 have been worn away), it is clearly visible that the actual teeth of the two crania are of
similar size, which implies that the relative tooth size of the H. habilis skull is larger (Figures
1 and 7).
Figure 9. Modern European Male skull (bottom)
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KNM-ER 1813 has much less foramina than the modern European male skull. Yet this might
be because the hominin cranium was too fragmented and damaged that it would be hard to
distinguish whether the dents are actually foramina.
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Cranial Measurements
Measurement KNM-ER 1813Modern European
Male
Glabella-occipital length 136 166Maximum cranial breadth 96.5 133
Basion-bregma height 89 136
Basion-nasion length 73.5 98
Nasion-prosthion height 54.5 62.7
Basion-prosthion length 91.9 95
Bizygomatic breadth 95-110* 122
Nasal height 36.5 48.5
Nasal breadth 23.4 25.4
Orbit height (right) 28.8 32.2
Orbit breadth (right) 32 38.9
Palate length 58.5 47.3Palate breadth (external) 58.4 61
Palate breadth (internal) 31.6 36.7
Nasion-occipital length 131.8 165
Nasion-bregma chord (Frontal chord) 75.9 116.5
Nasion-bregma arc (Frontal arc) 89 128
Bregma-lambda chord (Parietal chord) 83.3 105.1
Bregma-lambda arc (Parietal arc) 90.5 116
Lambda-opisthion chord (Occipital
chord)64.2 93.1
Lambda-opisthion arc (Occipital arc) 86 108Table 1. Cranial measurements of KNM-ER 1813 and the modern European male skull.
NOTE: All values are corrected to one decimal place.
* Because both cheeks are incomplete, hence an estimated range of bizygomatic breadth is
given.
Cranial Measurements: Interpretation and Comparison
The maximum cranial length (glabella-occipital length) and the maximum cranial breadth of
KNM-ER 1813 are both significantly shorter than the values of the modern European male
skull. When these values are substituted into the equation of the Cephalic Index:
Maximum cranial breadth*100
Maximum cranial length
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The indices for the hominin skull and the modern cranium are 71.0 and 80.1 respectively.
According this index, the hominin skull is categorised as a dolichocephalic (80). This means KNM-ER 1813 and
modern humans are significantly different as KNM-ER 1813 is long-headed, whereas modern
humans are broad-headed.
The basion-bregma height represents the cranial height. Comparing the basi-bregmatic height
of the two skulls, the cranial height of the modern cranium is much taller than that of KNM-
ER 1813. But when the maximum cranial length of the two crania are divided by their
respective cranial heights, the resulting value of the hominin cranium is larger, meaning that it
is in fact taller.
The basion-nasion length reflects the facial height regardless of face projection. KNM-ER
1813 has a much shorter face than H. sapiens. When the basion-nasion length is divided by
the upper facial height, nasion-prosthion height, it is discovered that the upper face takes up a
larger portion of the face (in terms of height) in both skulls than the lower face, and that the
upper face of the modern skull takes a larger portion of the face than the hominin skull.
The basion-prosthion length measures the facial projection. Although the value of the basion-
prosthion length of KNM-ER 1813 is slightly shorter than that of the modern human skull, its
degree of facial projection is actually much higher considering how small the hominin
cranium is.
The nasal height of KNM-ER 1813 is shorter than that of the modern cranium. Yet, when the
nasal heights of the two skulls are divided by their respective basion-nasion lengths (the facial
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height), two similar values are achieved, suggesting that the hominin individual possesses a
relatively bigger nose than modern human beings. When we divide nasal height using nasal
breadth, a bigger value is attained for the modern cranium, indicating that modern human
nose is more elongated than that ofH. habilis.
The right orbit of KNM-ER 1813 is used for measurement since the left orbit is crooked. The
height of the orbits of KNM-ER 1813 is slightly shorter than that of the modern cranium.
However, taking into account the facial height of both skulls, the orbits of the hominin
cranium are taller than those ofH. sapiens.
The palate length of the hominin skull is significantly longer than the modern one; whereas
the palate breadths of the two crania are similar.
Table 2 shows the results of frontal chord and parietal chord divided by the sum of the length
of both chords of respective crania. Despite the huge difference in the actual values of the
chords, the proportion of frontal and parietal of both skulls is quite similar.
Chords KNM-ER 1813Modern European
Male
Nasion-bregma chord (Frontal chord) 0.51 0.50
Bregma-lambda chord (Parietal chord) 0.49 0.50
Table 2. Results of frontal chord and parietal chord divided by the sum of the length of both
chords of respective crania.
Comparing the difference between the arcs and chords can give the degree of projection of
frontal, parietal and occipital areas. A larger difference is noted for the frontal of KNM-ER
1813. This implies that the frontal of the H. habilis skull is more protuberant than the frontal
of the modern European male cranium. The difference between the parietal arc and the
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parietal chord of the modern skull is bigger than that of the hominin cranium, suggesting that
the parietal of the modern skull is more projecting. The occipital area of KNM-ER 1813 is
more protruding, as indicated by the significantly larger difference between the occipital arc
and the occipital chord.
Conclusion
In spite of being in the same genus Homo, the two skulls are different in a lot of aspects. It is
through time that evolutionary changes develop gradually, turning us from H. habilis into
what we are today. Due to the poor preservation of KNM-ER 1813, many parts of the skull
cannot be compared with modern skulls and quite a few measurements taken on it may not be
fully accurate. It is hoped that later on some relatively more complete H. habilis skulls will be
excavated to help identify what the changes that took place during our evolution from H.
habilis toH. sapiens are.
Reference:
Leakey, R.E.F.
1974 Further evidence of Lower Pleistocene hominids from East Rudolf, North Kenya, 1973.
Nature 248:653-656.
Phenice, T.W. and N.J. Sauer
1977Hominid Fossils: An Illustrated Key. 2nd edn. Dubuque, Iowa: W. C. Brown Co.
Smithsonian Institution
n.d. KNM-ER 1813 [on-line]. Available from: http://humanorigins.si.edu/evidence/human-
fossils/fossils/knm-er-1813[Accessed 9 January 2012].
http://humanorigins.si.edu/evidence/human-fossils/fossils/knm-er-1813http://humanorigins.si.edu/evidence/human-fossils/fossils/knm-er-1813http://humanorigins.si.edu/evidence/human-fossils/fossils/knm-er-1813http://humanorigins.si.edu/evidence/human-fossils/fossils/knm-er-1813http://humanorigins.si.edu/evidence/human-fossils/fossils/knm-er-1813